Developing Nuclear Weapons

owensdj

Golden Member
Jul 14, 2000
1,711
6
81
Why is it so difficult for nations to develop nuclear weapons? You'd think that if the US could do it over 60 years ago, it would be pretty easy with modern technology.
 

BrownTown

Diamond Member
Dec 1, 2005
5,314
1
0
its not really all that hard, just takes tons of $$$ and a good amount of time. Problem is that once everyone figures out what you're doing they will all get mad at you.
 

f95toli

Golden Member
Nov 21, 2002
1,547
0
0
It is not hard and you do not need a lot of money.
However, you do you need plutonium or highly enrichted uranium (I don't remember the percentage 85-90% ?) and if you don't have that you have to make it (using natural uranium ore as a the raw material). Enriching uranium is quite expensive and it requires pretty sophisticated technology (if you want the process to be efficient, the processes used during the Manhattan project were VERY inefficient).
However, the same process used to enrich uranium for nuclear power plants can also be used to make weapons grade uranium.

 

Gibsons

Lifer
Aug 14, 2001
12,530
35
91
Originally posted by: f95toli
It is not hard and you do not need a lot of money.
However, you do you need plutonium or highly enrichted uranium (I don't remember the percentage 85-90% ?) and if you don't have that you have to make it (using natural uranium ore as a the raw material). Enriching uranium is quite expensive and it requires pretty sophisticated technology (if you want the process to be efficient, the processes used during the Manhattan project were VERY inefficient).
However, the same process used to enrich uranium for nuclear power plants can also be used to make weapons grade uranium.


I think the amount of enrichment you need depends on how much uranium you can put into your bomb. So you might need 20lbs if you're at 90% purity, but only 15 if you're at 95% (Yes, I'm just making up the numbers, but I think the idea is right in principle). IIRC, it's technically possible to get an explosion with unenriched uranium, but you'd need a few tons (literally) of it to reach critical mass. Conversely, if you want to build a really small bomb, you need really high purity - I think I read somewhere that U.S bombs were in the 90-95% range, while the fuel on U.S. subs is something like 99%, fuel for normal reactors around 30%.

Another issue with enrichment it can also consume vast amounts of power. Centrifuges are somewhat energy intensive, and you'll want a lot of very large ones, running almost constantly.

The other difficult part is in making an efficient device. I would think a "gun" assembly wouldn't be too hard, but to get good yields you'd want to go the implosion route, and that's very tricky.
 

BrownTown

Diamond Member
Dec 1, 2005
5,314
1
0
fuel for nuclear subs aint anywhere near 99%, why the heck would a ship ahve more concentrated fuel then a bomb? Its much less then 99%, and power reactors are 4%, not 30. As for the concentration of U235 to make a bomb, last I heard 20% is the lowest feasible enrichment, but since you want to make the bombs as small and powerfull as possible you want as high as you can get, somewhere ~90% like you said.
 

Gibsons

Lifer
Aug 14, 2001
12,530
35
91
Originally posted by: BrownTown
fuel for nuclear subs aint anywhere near 99%, why the heck would a ship ahve more concentrated fuel then a bomb? Its much less then 99%, and power reactors are 4%, not 30. As for the concentration of U235 to make a bomb, last I heard 20% is the lowest feasible enrichment, but since you want to make the bombs as small and powerfull as possible you want as high as you can get, somewhere ~90% like you said.

Weight and space are at a huge premium on a submarine. And I was working from memory, not Googling. :p
HEU is also used in nuclear submarine reactors, where it contains at least 50% 235U, but typically exceeds 90%.

Text, if you believe wiki.

 

BrownTown

Diamond Member
Dec 1, 2005
5,314
1
0
still, aint gonna be 99%, though 90% is more than I would have thought, would have estimated ~50, not 90, thats pretty hard core.
 

Spinne

Member
Sep 24, 2003
57
0
0
Originally posted by: Gibsons
Originally posted by: f95toli
It is not hard and you do not need a lot of money.
However, you do you need plutonium or highly enrichted uranium (I don't remember the percentage 85-90% ?) and if you don't have that you have to make it (using natural uranium ore as a the raw material). Enriching uranium is quite expensive and it requires pretty sophisticated technology (if you want the process to be efficient, the processes used during the Manhattan project were VERY inefficient).
However, the same process used to enrich uranium for nuclear power plants can also be used to make weapons grade uranium.


I think the amount of enrichment you need depends on how much uranium you can put into your bomb. So you might need 20lbs if you're at 90% purity, but only 15 if you're at 95% (Yes, I'm just making up the numbers, but I think the idea is right in principle). IIRC, it's technically possible to get an explosion with unenriched uranium, but you'd need a few tons (literally) of it to reach critical mass. Conversely, if you want to build a really small bomb, you need really high purity - I think I read somewhere that U.S bombs were in the 90-95% range, while the fuel on U.S. subs is something like 99%, fuel for normal reactors around 30%.

Another issue with enrichment it can also consume vast amounts of power. Centrifuges are somewhat energy intensive, and you'll want a lot of very large ones, running almost constantly.

The other difficult part is in making an efficient device. I would think a "gun" assembly wouldn't be too hard, but to get good yields you'd want to go the implosion route, and that's very tricky.



For a viable energy release during disassembly you need th insertion time to be two or three orders of magnitude smaller than the device disassembly time. The larger your device is, the larger your insertion time gets. That puts a cap on how big (literally in size) you can make a fission device.
 

Spinne

Member
Sep 24, 2003
57
0
0
Hurdles that need to be overcome are
1)U235 enrichment (U238 has only marginaly different physical properties to U235)
2)U to Pu conversion in a reactor (not that hard)
3)Gun type devices using U are reltively simple, but have a very low max yield. The insertion time for a gun type devceis too large for Pu, so for Pu you need an imploding sphere. For this, you need to figure out how to make explosive lenses to generate a controlled compressive wave.
4)To set your lenses off, you need very very high speed, high reliability, high power switches. The high power, high speed requirement is the real killer. You need to learn how to design and fabricate hese yourself, since thier export is very controlled (more so than the fissile materials themselves).
In the end, the Physics isn't hard, it's the chemical, mechanical ad electrical engineering that is hard to do.
 

allenthehobo

Junior Member
Apr 15, 2006
3
0
0
1) Money. Before the U.S. developed the bomb, nuclear fission was widely known; it just took a ginormous amount of money to research the stuff. Not many countries are as rich as the U.S. (Then again, not many countries are in as much debt as we are, either... =/)

2) Materials. You need uranium. You need the materials to seperate the right uranium from the wrong uranium (U-235 from U-234, I think?), or plutonium. You need the scientists who can do this. + you need extreme preciscion in making the bomb, because if you don't, it'll go... badly.

3) International pressure. Right now, everyone hates nukes, and if you try to develop them, everyone will hate you. Look at North Korea and Iran. And with all the modern technology, all the nuclear fuel and whatnot is tracked a lot easier, so you'll know exactly where the nuclear stuff is, and if anyone's looking out to buy some.



 

stelleg151

Senior member
Sep 2, 2004
822
0
0
Originally posted by: allenthehobo
1) Money. Before the U.S. developed the bomb, nuclear fission was widely known; it just took a ginormous amount of money to research the stuff. Not many countries are as rich as the U.S. (Then again, not many countries are in as much debt as we are, either... =/)

2) Materials. You need uranium. You need the materials to seperate the right uranium from the wrong uranium (U-235 from U-234, I think?), or plutonium. You need the scientists who can do this. + you need extreme preciscion in making the bomb, because if you don't, it'll go... badly.

3) International pressure. Right now, everyone hates nukes, and if you try to develop them, everyone will hate you. Look at North Korea and Iran. And with all the modern technology, all the nuclear fuel and whatnot is tracked a lot easier, so you'll know exactly where the nuclear stuff is, and if anyone's looking out to buy some.

I would say #3 is the biggie really. IIRC europe has much more nuclear based energy, with which one can create uranium (is done in the recycling of nuclear waste), but it isnt "allowed" by the UN because nobody wants uranium around that could be stolen by terrorists.

Basically it is the US is desprately trying to control it. Look at Iraq, we jumped in without even having conclusive evidence... (definately possibility: other motives), and we have around 40,000 troops waiting in south korea at the border antsy to rip north korea a new one if they so much as breathe in the wrong direction.

In the words of Rumsfeld: "Bring it on, we can take them all"